public class CircleTest {

    public static void main(String[] args) {
        Circle circle = new Circle();

        circle.r  = 1000;
        circle.area();

        double pai = 3.1415926;
        double s= circle.area2(pai);
        System.out.println("半径为" + circle.r + "的圆，面积为" +s );
    }
}
